Pulmonary diffusing capacities for oxygen-labeled CO2 and nitric oxide in rabbits.
We determined the pulmonary diffusing capacity (DL) for 18O-labeled CO2 (C18O2) and nitric oxide (NO) to estimate the membrane component of the respective gas conductances. Six anesthetized paralyzed rabbits were ventilated by a computerized ventilatory servo system. Single-breath maneuvers were automatically performed by inflating the lungs with gas mixtures containing 0.9% C18O2 or 0.05% NO in nitrogen, with breath-holding periods ranging from 0 to 1 s for C18O2 and from 2 to 8 s for NO. The alveolar partial pressures of C18O2 and NO were determined by using respiratory mass spectrometry. DL was calculated from gas exchange during inflation, breath hold, and deflation. We obtained values of 14.0 +/- 1.1 and 2.2 +/- 0.1 (mean value +/- SD) ml.mmHg-1.min-1 for DL(C18O2) and Dl(NO), respectively. The measured DL(C18O2)/DL(NO) ratio was one-half that of the theoretically predicted value according to Graham's law (6.3 +/- 0.5 vs. 12, respectively). Analyses of the several mechanisms influencing the determination of DL(C18)2 and DL(NO) and their ratio are discussed. An underestimation of the membrane diffusing component for CO2 is considered the likely reason for the low DL(C18O2)/DL(NO) ratio obtained.
Heller
H
H
Department of Physiology, University of Bonn, Germany.
Fuchs
G
G
Schuster
K D
KD
D000818:Animals; D002245:Carbon Dioxide / Q000502:physiology*; D013058:Mass Spectrometry; D009569:Nitric Oxide / Q000502:physiology*; D010103:Oxygen Isotopes; D010313:Partial Pressure; D011653:Pulmonary Diffusing Capacity / Q000502:physiology*; D011817:Rabbits; D012121:Respiration, Artificial; D012129:Respiratory Function Tests
D010103:Oxygen Isotopes; D002245:Carbon Dioxide; D009569:Nitric Oxide